Conventionally, quantum dots made of silicon have been formed using an LPCVD (Low Pressure Chemical Vapor Deposition) technique (Japanese Patent Application Laid-Open No. 2006-32564).
In other words, the quantum dots are formed by using a silane (SiH4) gas as a material gas, and performing a reaction for 50 to 70 seconds at a reaction pressure of 0.5 Torr and at a substrate temperature of 560° C. to 600° C.